Transfer half of the heads to a non-metallic bowl and add a layer of coarse sea salt. Follow with the rest of the seed pods and again cover with the coarse sea salt. Set aside at room temperature.
For the next four days let the seed pods cure in the salt, giving them a mix each day.
After four days, wash off the salt from the seed pods and pat dry.
In a pot add apple cider vinegar, sugar and salt and bring to a rapid boil. Once the sugar and salt have dissolved, remove from heat and cool.
In a sterilised jam jar, add the seed pods and pour over the cooled pickling liquor. Seal the jar with the lid and refrigerate.
After three to four days the capers are ready for use.